PROJECT SUMMARY Children with ?high-risk? leukemia receive intense treatments that, while life-saving, can also cause them to develop problems with the way they learn and think. This does not happen to all children receiving these treatments, but we cannot yet predict who will develop problems. One reason that we lack this information is that it is often difficult to test changes in the way children learn while they are receiving medical treatment. Children may feel too sick to complete testing, psychologists are not always available to do the evaluations, and insurance companies may not cover the testing that is needed. In this project, we aim to identify the first signs of changes in thinking and learning using a short, computerized testing program. The tests can be given in clinic by nurses or other staff, and cost very little money. We will test children starting shortly after leukemia is diagnosed, and several times during the course of their treatment, so that we can identify problems as soon as they start to occur. Children in our study will also receive a one-hour evaluation with widely-used tests of learning and memory, given by a psychologist, five years after their diagnosis. We will determine whether results from the computerized tests are able to predict performance on the more traditional tests given by the psychologists. If computerized testing done early in treatment helps us to better predict who will go on to have difficulties, we can help to slow down or eliminate these problems. Finally, we want to determine the extent to which other factors also contribute to problems that develop as a result of leukemia treatment. We are especially interested in looking at factors known to affect children's thinking and learning skills, like a family's access to resources, mental health difficulties, and medical problems that can occur during treatment. We will also be asking children to tell us about how tired, sick, or in pain they are right before they complete the computerized testing program. Because there is some evidence indicating that these types of symptoms may affect children's performance on cognitive tests, we believe that it's important to describe any impact that these symptoms have on children's thinking and learning, both early in treatment and also much later. If we can better understand how all of these factors relate to survivors' patterns of thinking and learning, we can better predict which individuals may be affected by those problems.